Synthesis and properties of sulfonated poly(ether ketone)s containing 3,5-dimethyl phthalazinone moieties as proton exchange membrane materials

Sulfonated poly(ether ketone)s containing 3,5-dimethyl phthalazinone moieties (SPPEK-DMs) with different degrees of sulfonation (DS) were synthesized via direct polycondensation from 4-(3,5-dimethyl-4-hydroxyphenyl)-2,3-phthalazinone, 4,4'-difluorobenzophenone and 3,3'-disulfonate-4,4'-difluorobenzophenone. The chemical structure of SPPEK-DMs was characterized by FTIR and 1H-NMR. Thermal stability of SPPEK-DMs was characterized by the thermogravimetric analysis. The membranes prepared from SPPEK-DMs exhibited ion exchange capacities (IEC) ranging from 0.93 mmol center dot g(-1) to 1.86 mmol center dot g(-1). Water uptake, swelling, oxidative stability and methanol permeability of SPPEKDMs membranes were investigated. SPPEK-DMs membranes exhibited high oxidative stability. The methanol permeability values of SPPEK-DMs membranes were in the range 5.15 x 10(-8)-6.61 x 10(-7) cm(2)center dot s(-1), which was much lower than those of Nafion117. The proton conductivity of SPPEK-DM40 membranes was 1.1 x 10(-2) S center dot cm(-1) at 70A degrees C.